TAMPA, Fla. (AP) — In a presidential campaign filled with sharp criticism, this may be Mitt Romney's softest sell: persuading people who voted for Democrat Barack Obama and now have some buyer's remorse to back the Republican instead.

"We led with our hearts and our dreams that we could be more inclusive than America had ever been, and no candidate had ever spoken so beautifully," former Democratic Rep. Artur Davis of Alabama, who recently switched parties, told the Republican National Convention. "But dreams meet daybreak."

Davis, who seconded Obama's nomination at the Democratic National Convention in Denver in 2008, was the personification Tuesday of a bloc of voters who backed Obama four years ago but who now are disenchanted.

Romney is trying to lure these voters into his fold, and courting them was a theme of the first full night of his national nominating convention.

Republican nominee Romney is taking care not to insult these voters, whose support could be critical in key states where the race is tight. He is gently asking them to reconsider their past support of Obama, if they're not already.

"Ask one more person to join us, who supported President Obama four years ago and didn't get the change they deserved," Romney told an audience in Chillicothe, Ohio, this month.

He featured some of these disillusioned Obama voters in a short video at the convention Tuesday.

Among them: Debbie Smith of Iowa. "As the co-owner of a small business, I'm not supporting Barack Obama this time because I just don't see things getting better," Smith says in the video.

The 51-year-old from Des Moines helped launch Obama on the path to the presidency. The lifelong Democrat supported him in the 2008 Iowa caucuses, which Obama won. The win established him as the Democratic front-runner.

But Smith was unimpressed with Obama's handling of the debate over federal health insurance legislation in 2009 and then came to think he was not taking the growing federal debt seriously.

Like millions of voters in 2008, Smith had hoped in voting for Obama that his call for bipartisanship in a bitterly divided political environment would come to pass. Obama was able to cobble together a coalition of voters that also included disaffected Republicans turned off by the Bush administration's spending patterns.

Smith is not angry, just disappointed in changes she did not expect.

"I don't want to tell people who to vote for," Smith said in an interview. "I just want people to do their homework."

Romney's campaign is hoping to win over people like Smith in battleground states such as Iowa and Ohio, where the race is viewed as very close.

Iowa is symbolic because, after Obama won the caucuses, he carried the state in the general election by 9 percentage points, the biggest winning margin there in a quarter-century.

Romney's hoping he can also lure back those independents and moderate Republicans who walked away from the GOP for Obama.

Iowa is one of seven states where polls show neither Obama nor Romney has a significant advantage. The others are Ohio, Colorado, Florida, Nevada, New Hampshire and Virginia.

Another member of that voter group Romney's trying to lure is Ashley Bell of Georgia.

The lawyer was an Obama supporter in 2008. His wife, Lauren, was a delegate to the Democratic convention that year.

He said he respected that Obama, as a candidate, opposed requiring all Americans to obtain health insurance, a position he would change in signing the 2010 health care law, which includes a health insurance mandate.

Bell, who is African-American, said he voted for Obama because he viewed the Democrat as a pragmatist. He did not support Obama because he is black, although he was proud to back the first black president.

"We were excited in the moment. And we still have an affinity for the guy," Bell said. "But we had to look at the big picture."

Aides to Obama's campaign declined to comment about the Romney campaign's effort to woo the Democrat's past supporters. But they noted that Davis, who served four terms in the House, voted with Democrats 95 percent of the time before he left Congress in 2010.